1. Field of the Invention
This invention relates generally to automated data-storage libraries and, in particular, to a lockout mechanism for ensuring that a data cartridge is inserted correctly into the receiving cell of the input/output station of a library.
2. Description of the Related Art
The portability of magnetic tape cartridges makes it possible to store them in readily accessible multi-cell libraries, so that large amounts of data can be saved and retrieved at will using automated equipment. When, for example, a particular cartridge is required for use in a computer's I/O device, the unit is retrieved by a robot from the cell where it has been stored in a library and it is automatically loaded for processing.
Cartridges are initially placed into libraries manually through input/output stations which consist of stacks of individual through-slots with an exterior opening adapted to receive a cartridge of a predetermined size and configuration. For example, FIG. 1 illustrates an IBM 3584 Automated Library that incorporates an I/O station 10 with a cartridge 12 inserted half-way into a receiving through-slot 14. Each slot has also an interior opening (not shown) through which the cartridge is removed by a robot for automated placement in a library storage cell or drive. The picker mechanism through which each cartridge is transferred includes gripper arms that hold the cartridge and guide it in and out of the I/O station, and similarly in and out of the library cell, computer peripheral, or other device being used. The cartridges have retaining features that permit gripper arms to latch on to the cartridge by means of appropriate locating and gripping notches or equivalent structural features built into the case of the cartridge. Accordingly, commercial cartridge formats are standardized to provide uniformity of construction and interchangeability of operation between cartridges produced by different manufacturers.
In operation, each cartridge 12 is initially inserted manually by an operator into a slot 14 of a receiving cell in the I/O station. The cartridge must be positioned correctly in order for the gripper arms to be able to retrieve it from the other side of the cell. Thus, only one of the eight sides of a conventional cartridge is acceptable for the picker mechanism inside the library and any other orientation of the cartridge would be incorrect and cause a failure of the automated system. The problem is worse with libraries that operate with multiple types of cartridges and that, therefore, provide an even smaller ratio of correct options. If two formats are used, for example, only one out of sixteen possible alternatives is correct.
Two of the cartridge formats most widely used currently around the world are the so called DLT (digital linear tape) and LTO (linear tape open) formats, each characterized in detail by corresponding ECMA (European Computer Manufacturers Association) 286 and 319 standards. Accordingly, IBM's 3584 Library accommodates both types of cartridge and is equipped with corresponding I/O units with cells selectively dedicated to one cartridge or the other. Each cartridge format features prescribed structural attributes adapted to function with conforming standard features in the automated mechanisms of a corresponding drive, picker and library system. For example, a typical DLT format cartridge 20, such as IBM®'s DLTtape® IV Cartridge illustrated in FIG. 2, is characterized by a hinged door 22 on the front side 24 of the cartridge. When the DLT cartridge is inserted into a drive, a stationary device penetrates a gap 26 in the door hinge 28 and presses against a spring-loaded latch 30 to automatically release the door 22 and swing it open toward the front of the cartridge. As a result, the tape's leader inside the cartridge (not seen) can be accessed by the drive's mechanism. As the door 22 opens, the door hinge 28 rotates inwardly toward the right side 32 of the cartridge. Accordingly, the right side of the DLT cartridge 20 features a progressively deepening cavity 34 designed to accommodate the door hinge 28 when the door 22 is fully open. The shallower portion of the cavity 34 also features two side ribs 36.
Thus, the right side 32 of the DLT cartridge contains several pronounced structural features that distinguish it from all other sides, as well as from every side of the LTO cartridge. When a DLT cartridge is inserted in an I/O station by an operator, it must be placed top-side up and with the door 22 facing the exterior of the station, as illustrated in FIG. 3; otherwise, the library picker cannot properly grab and retain the cartridge, and the picker may become disabled causing the automated library to go off-line and the stored data to become unaccessible. This possibility of failure is unacceptable in today's world of uninterrupted-service demand. Therefore, it would be very desirable to have a mechanism that prevents the incorrect placement of a DLT cartridge or the placement of another cartridge into the receiving slots of an I/O station designed to handle only DLT cartridges.
U.S. Pat. No. 6,141,180 describes a pivoting lockout that prevents the incorrect placement of a DLT cartridge into a receiving device, such as a tape magazine, a library or a mail slot. The lockout consists of a hinged member with a leading and a trailing edge protruding into the sleeve to be occupied by the cartridge when it is placed in the receiving device. Therefore, the cartridge can be successfully introduced into the device only one way, when the side containing the cavity is facing the hinged lockout member. Because of its configuration and placement, the lockout member is able to clear the ribs 36 and to fit into the cavity 34 of the DLT cartridge (refer to FIG. 2 above) as the cartridge is pushed into the sleeve of the receiving device. Thus, the lockout of the invention prevents the complete insertion of the DLT cartridge unless it is oriented correctly.
The Smith lockout device is not designed for a pass-through sleeve of the type present in I/O stations. It is only concerned with ensuring that the cartridge is placed correctly in a receiving cell from which it is to be extracted later in reverse direction. Accordingly, the door hinge 28 could not clear the two protruding edges of the lockout if the cartridge were to be extracted in pass-through fashion from the interior side of an I/O station. The present invention provides a new design for a lockout mechanism that overcomes this problem and is therefore suitable for use in input/output stations.